What is the variant of the minimax tree with 3 types of nodes called?
The triangles pointing up are Max' nodes. We assume it starts. Then follows a random choice of moves at the circles, for instance, with a die. The triangles pointing down are from Min. This variant is called Expectiminimax, see https://en.wikipedia.org/wiki/Expectiminimax_tree.

At that circles you have to multiply the possibilities on the edges below that nodes to your current value and sum all products up. The circles in your picture mean that Min dices.